FIELD OF THE INVENTION
The invention relates to a one-piece contact spring having a box-shaped contact part, onto which a bottom wall and a top wall are formed, from each of which a spring arm is bent backward on the insertion end into the interior of the contact part, wherein the spring arms extend toward one another and are provided on their ends with freely resilient rounded contact points, and having a connection part, formed onto it opposite the insertion end.
Contact springs are widely used as plug connector, in automotive engineering, for instance, and often have two parts that have to be made separately from one another, namely a bottom spring and a top spring, or locking sleeve, that has to be folded over onto the bottom spring. On its end toward the insertion end of the contact spring, the bottom spring has two spring arms, onto whose end remote from the insertion end of the contact spring a connection part for an electrical conductor is formed integrally. The bottom spring is preferably a stamped and bent part and because of the requisite good electrical property it preferably comprises tin-plated brass, tin-plated copper, or so-called spring bronze. The top spring that is to be folded over onto the bottom spring has the function essentially of increasing the spring force of the contact spring, and by embodying it with one or more detent tongues of enabling a releasable locking of the contact spring in a contact chamber of a housing made of insulating material. The releasable locking of the contact spring by such detent tongues is also called primary locking. As a rule, the top spring comprises a material with good spring properties and can likewise be made as a stamped and bent part. Sheet metal, for instance, is a suitable material.
Contact springs having two elements that have to be made separately from one another, namely the grand the top spring, have the disadvantage that relatively major effort must be expended to secure the top spring on the bottom spring in a slip-proof manner. Moreover, the known contact springs having bottom springs and top springs fitted over them are relatively expensive in terms of both materials and the effort of assembly.
Less expensive, one-piece contact springs have also been disclosed, however. One such one-piece contact spring is shown for instance in the two references, U.S. Pat. No. 4,152,042 and French patent disclosure FR A 2 157 490. In both references, box-shaped contact parts of a contact spring are described that have spring arms bent backward into the box interior.
FR-A 2 157 490 describes a box-shaped contact part of a contact spring that either has spring arms bent back from each of the four side walls, or only two spring arms bend back opposite one another. In the exemplary embodiment described there that has the four spring arms bent back into the box interior, these arms rest flatly on the associated side wall over a relatively long region and are then bent obliquely inward over the remainder of the length. In the exemplary embodiment described there having only two spring arms bent back into the box interior, the spring arms are approximately V-shaped, and they rest with their ends on the associated inner walls of the side walls again. The opposed spring arms are spaced relatively far apart from one another. Because of the relatively wide spacing of the spring arms from one another, a satisfactory connection with an introduced plug contact is possible, with these contact springs, only if the plug contact has an adequate thickness or width. If a too-small plug contact is introduced into this contact spring, then only a very poor contact or none at all is possible.
In U.S. Pat. No. 4,152,042, a contact spring is described which is improved by comparison. The contact spring is distinguished by two spring arms bent back into the box interior from two opposed side walls. The spring arms are bent backward 180 from the attached side walls and then extend toward one another in curved fashion. The free ends of these spring arms are provided with rounded contact points facing one another at a relatively close distance, which enable a secure plug connection even if a small pug contact is plugged in. To relive the bend of the two spring arms, the spring arms are provided with a recess on the inside, in the region of the bend. As a result, greater elasticity of the bend is attained. However, beginning at the bend, the spring arms extend toward one another in curved fashion. This necessarily means that the bend is stressed relatively severely when a plug contact is introduced into the contact spring and the ends of the spring arms are thus forced apart. The result, under some circumstances, can be damage or breakage of the contact spring at the bent points.